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Hole Hopping through Cytochrome P450.

Mette L H Sørensen1, Brian C Sanders2, L Perry Hicks3

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Summary
This summary is machine-generated.

High-potential iron-oxo species in oxygenase enzymes can damage cells. A protective mechanism involving tryptophan (Trp) and arginine (Arg) in cytochrome P450s appears conformationally gated, not electronically driven.

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Area of Science:

  • Biochemistry
  • Enzymology
  • Protein Science

Background:

  • Oxygenase enzymes utilize high-potential iron-oxo species as intermediates.
  • These intermediates can lead to heme degradation and amino acid oxidation.
  • A proposed protective mechanism involves hole hopping through tryptophan/tyrosine chains.

Purpose of the Study:

  • To investigate the role of the Trp96/Arg398 cation-π interaction in cytochrome P450 protective mechanisms.
  • To determine the effect of this interaction on Trp96 redox potentials and heme electronic coupling.
  • To assess the impact of mutations on phototriggered electron transfer rates.

Main Methods:

  • Site-directed mutagenesis of cytochrome P450 (Arg398His).
  • Measurement of Trp96 formal potentials.
  • Calculation of electronic coupling strengths between Trp96 and the heme.
  • Phototriggered electron transfer studies using a Ru-sensitizer.

Main Results:

  • Mutation of Arg398 to His decreased the Trp96 formal potential and increased Trp-heme electronic coupling.
  • Phototriggered electron transfer rates were unexpectedly unaffected by the Arg398His mutation.
  • Trp96 was found to move away from Arg398 in the mutant.

Conclusions:

  • The protective mechanism involving the Trp96/Arg398 pair in P450s is likely conformationally gated.
  • Electronic effects alone do not fully explain the protective function.
  • Structural rearrangements play a crucial role in enzyme protection.